Radiant heater

ABSTRACT

A radiant heater having a trough-shaped reflector comprising a plurality of elongated planar sections joined edge to edge in such angular relationship that the trough has a substantially parabolic contour in transverse cross section. The sections immediately adjacent to and on either side of the vertex of the parabola are bent to form an inwardly directed V-shaped rib which reflects heat rays away from an elongated heat generating element positioned at the focus of the parabola. The reflector is housed within an outer shell in spaced relationship thereto, the space between the two being open to the atmosphere along the lateral edges of the reflector and via apertures located in the central section of the shell.

ltinitei States Patent 1191 Rohats 1 1 May 15, 1973 [54] RADIANT HEATER FOREIGN PATENTS OR APPLICATIONS Inventor: Frank J- R9hats,KaI1SaSCit1/, 816,720 10/1951 Germany ..219 354 253,365 7/1926 Great Britain ..219/347 [73] Asslgnee' Rwmhpoweu Kansascty 543,671 12 1955 Belgium ..219/347 [22] Filed: May 26, 1971 1,120,122 4/1956 France ..219/356 1,112,319 11 1955 F 21 Appl.No.: 146,877 I 219/354 Primary ExaminerA. Bartis 1521 U.S. c1. ..219/343, 219 342, 219/347, m y-scofield, Kokj r, S ofiel & Lowe 219/357, 240/47, 240/103 B, 250/89 [51] Int. Cl ..H05b 1/00, F21v 7/12, F2lv 29/00 [57] ABSTRACT 58 Field is h 219 339-343, 1 0 care 3464,58 377 24o/{O3B 47 A radiant heater having a trough-shaped reflector 103 250/85 86 comprising a plurality of elongated planar sections joined edge to edge in such angular relationship that [56] References Cited the trough has a substantially parabolic contour in transverse cross section. The sections immediately ad- UNITED STATES PATENTS jacent to and on either side of the vertex of the l 418 671 6/1922 parabola are bent to form an inwardly directed V- l332052 2/1920 shaped rib which reflects heat rays away from an elon- 1:393:363 10/1921 gated heat generating element positioned at the focus 3 217 139 11 19 5 of the parabola. The reflector is housed within an 1,109,551 9/1914 outer shell in spaced relationship thereto, the'space 3,143,629 8/1964 between the two being open to the atmosphere along the lateral edges of the reflector and via apertures 3:371:12 2,1968 located in the central sectlon of the shell. 2 Claims, 4 Drawing Figures I a" I x /a 4? 12 1 J2 2 ,4 6 g 4" R; 0 I4 a F o /6 1 w x a /04 4 A25 1 1 g i /7 /0e 4 l 0f \M 0e /9 I t .e emJ unis- 4 l 1 20 5a--..) Y a 4 0' /a PATENTEB MAY 1 51973 Frank J: 6 0/2078 RADIANT HEATER BACKGROUND AND SUMMARY OF THE INVENTION The advantages of a basically parabolic reflecting surface for radiant heaters have, of course, been known for some time. In spot heating applications, for example, the parabola has a distinct advantage in that by cating the heating element at the focus of the parabola, all heat rays are reflected parallel to the axis of the parabola. This means that the rays can be directed in a substantially defined path with minimum heat scattering or loss to the surrounding environment.

One serious difficulty with parabolic reflectors, however, has been that the vertex region reflects heat back directly onto the heating element itself, tending to cause the element to overheat and thus burn out more quickly than would otherwise be the case. In order to prolong the useful service life of the element and avoid the need for frequent replacement, it often has been necessary to operate. the unit at less than peak output, thus reducing the efficiency and capacity of the heater.

Again, with an elongated rod-type heating element mounted in a trough-shaped reflector having a parabolic cross section, temperature changes accompanying heat-up or cool-down often introduced stresses that resulted in distortion or warping of the reflector.

It is the object of the present invention, broadly speaking, to provide an improved radiant heater that overcomes the disadvantages and difficulties mentioned above.

More specifically, one of the objects of the invention is to provide an elongated trough-shaped heat reflector of generally parabolic cross section, which has improved stability and rigidity.

Another object is to provide a heat reflector of the foregoing character, which has means for deflecting reflected heat away from the heating elements so that the element can have a substantially higher heat generating capacity without-shortening its life expectancy.

Still another object is to provide, in conjunction with a reflector of the foregoing character, of cooled exterior shell or cover of improved construction, for rigidly supporting the reflector and protecting it from physical injury or deformation, while at the same time safeguarding those in the vicinity of the heater from injury due to accidental contact with the hot reflector.

All of these objectives are achieved according to the invention in an efficient yet simple way.

The trough-shaped reflector is formed by bending a flat metal sheet into a series of planar sections that are angularly disposed with respect to one another so as to provide their own reinforcing means, the finished cross-sectional contour of the reflector nevertheless being substantially parabolic. Included in the reflector at the vertex of the parabola is a V-shaped segment that deflects heat away from a rod-type heating element located at the focus of the parabola. Additionally, provisions are included for improving the circulation of air in the chamber separating the reflector from its outer shell, thereby reducing the heat transferred to the outer shell.

Other and further objects of the invention, together with the features of novelty whereby the objects are achieved will appear in the course of the following description.

DESCRIPTION OF THE DRAWING In the accompanying drawing, which forms a part of the instant specification and is to be read in conjunction therewith, like reference numerals are employed to indicate like parts in the various views.

FIG. 1 is a bottom plan view of a radiant heater embodying my invention, part of the heating element being broken away for purposes of illustration;

FIG. 2 is a longitudinal cross section of the heater taken along the line 2-2 of FIG. 1 in the direction of the arrows;

FIG. 3 is a top plan view of the heater; and

FIG. 4 is an enlarged transverse cross section of the heater taken along line 44 of FIG. 1 in the direction of the arrows.

Referring more particularly to the drawings, the radiant heater shown therein has an inner reflector 10 and an outer shell or housing 12, both generally troughshaped, with an air space 14 therebetween.

The main body of the outer shell is formed of a single piece of sheet metal bent as shown in FIG. 4 to form a central flat top portion 12a joined to the side walls 12b by downwardly diverging wall panels 120, each side wall having at its lower edge an in-turned flange 12d extending the full length of the shell. The two ends of the shell are closed by end panels 12e which conform to the contour of the main body of the shell and are secured thereto by welding or in any other suitable manner.

Mounted within the outer shell or housing 12 is the reflector 10 which is approximately parabolic in transverse cross section. More specifically, the main body of the reflector is formed of a single piece of flat sheet metal bent along laterally spaced parallel lines to provide planar reflecting surfaces 10a, 10b, 10c and 10d extending lengthwise of the reflector, and a pair of outtumed mounting flanges 10c also extending. the full length of the reflector. As will be understood, the planar sections 10a, 10b and adjoin one another in such angular relationship that they are substantially tangent to a parabola having its focus at 16 (FIG. 4) while the sections 10d depart from the general parabolic'configuration in that they are bent inwardly relative thereto to form a V-shaped rib running lengthwise of the reflector along its center line. At opposite ends of the reflector there are flanged reinforcing plates 10] which are welded, riveted or otherwise suitably secured to the main body of the reflector. All inner surfaces of the reflector are, of course, polished to a smooth mirror-like reflective finish.

Inverted in position, the trough-shaped reflector 10 is securely mounted within the outer shell 12 by means of its out-tumed flanges 10e, each of which overlaps a corresponding in-turned flange 12d of the shell, as indicated in FIG. 4. The flanges are apertured to receive fastening screws 18 on which are threaded nuts 19, each screw being encircled by a spacing collar or bushing 20 interposed between the confronting faces of the flanges to maintain them in spaced relation when the screws are tightened down. Thus, along each lower edge of the reflector there is a protected lateral passageway 22 via which air can freely enter or leave the space 14 between the shell and reflector. This space also is open to the surrounding atmosphere via a double row of apertures 24 located in the upper portion of the shell as shown in FIG. 3.

A conventional rod-type heating element 26 is mounted in the reflector by means of brackets 28 near the ends thereof. Each mounting bracket comprises a pair of opposed V-shaped jaws 28a and 2812 having the heating element removably clamped therebetween, the upper jaw having an integral vertical stem 28c which is flanged at its upper end and suitably secured to the reflector by welding or otherwise. The lower jaw or clip 28a is attached by simple fasteners, such as nuts 30 and bolts 32, which can easily be removed when it is necessary to replace the heating element 26.

The heating element conveniently can be, for example, a quartz tube containing a resistance wire coiled in a helix coaxial with the tube. The electrical connections to the heating element are conventional and have been omitted from the drawings in the interest of simplicity and clarity, but in practice the necessary wires are passed through suitably located apertures 34 in the reflector.

As previously suggested, the mounting bracket 28 is so constructed and arranged as to hold the heating element 26 at or very near to the focus of the parabolic envelope formed by reflecting surfaces a, 10b and 100. Thus, as illustrated by dashed lines in FIG. 4, the heat rays which these surfaces received directly from the element 26 are reflected downwardly in approximately parallel lines with comparatively little scattering or lateral spread.

However, the rays which impinge on the V-shaped rib formed by surfaces 10d are not reflected vertically downward (in which case they would contribute to overheating of the element 26) but instead are diverted laterally so as to clear the heating element. To this end, the V-shaped rib should be at least as wide as the diameter of the heating element 26, but preferably is not more than double said diameter. It also is preferred that said planar sections 10d meet in an obtuse angle which gives the rib a comparatively shallow V-configuration; the rib can, for example, be an approximate inversion or mirror image of the parabola in its vertex region.

A heating element 26 of the quartz tube type commonly is designed to operate in a temperature range between l,500 F. and 1,800 F., but when positioned in the path of the reflected heat rays such elements are subject to heat build-up which has a ruinous effect in terms of shortening their service life; or alternatively they must be operated with reduced efficiency at lower temperatures in order to offset or compensate for the heat build-up occasioned by the reflection. The heat deflecting feature of the V-shaped rib 10b thus plays a significant role in insuring efficient and economical operation of the heater at full capacity without sacrificint its service life.

The angular relationship of the individual flat sections 10a, 10b, 10c, 10d and l0e inherently serves to reinforce and strengthen the reflector as previously mentioned. The reflector is rigid and dimensionly stable so that, as the unit heats up, its essentially parabolic contour is maintained and the warping so often experienced with the conventional curved parabola is essentially eliminated.

The air circulation in the space 14 is important in cooling both the reflector l0 and the shell 12 and in maintaining a substantial temperature differential between the two. The reflector may reach a temperature of 500 F. and it is manifest that if the outer shell 12 were to approach this temperature it would be dangerous for personnel in the area who might come in contact therewith. For ceiling or wall-mounted units, it would also present a fire hazard. Therefore, by providing a circulation path for air, the heat transfer between the reflector is greatly minimized, enhancing the safety of the heater. Also, it will be noted that the innermost edges of the flanges 12d on the shell are spaced outwardly from the path of the rays reflected by the reflector 10 so as to avoid heating of the flanges by said rays.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinbefore set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the appended claims.

Inasmuch as various possible embodiments of the invention may be made without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. In a radiant heater, a trough-shaped outer shell having inwardly directed flanges along the lateral edges thereof, said outer shell also having a plurality of vent openings therethrough, a trough-shaped reflector having outwardly directed flanges along the lateral edges thereof, said reflector including said flanges being within the trough formed by said shell and the flanges on said reflector being overlapped by the flanges on said shell, the surfaces of said reflector being spaced from the surfaces of the outer shell to form an air space therebetween, said reflector being positioned in said outer shell so as to reflect radiation through the open face of the trough-shaped outer shell, means securing each reflector flange to its adjacent overlapping flange on the shell, said last means comprising fasteners spaced at intervals along the length of said flanges, each fastener including a spacer positioned between the confronting faces of said flanges to maintain same in spaced relation to form lateral air inlet passageways between the spacers whereby air may flow into the space between the outer shell and reflector and thence out through the vent openings in the outer shell, the innermost edges of the flanges on said shell being spaced laterally outward from the innermost edges of the flanges on said trough-shaped reflector, said reflector comprising a unitary metal sheet bent along laterally spaced parallel lines to form elongated planar reflecting surfaces joined edge to edge in such angular relation that said reflector is approximately parabolic in transverse cross section, and the planar reflecting surfaces immediately adjacent to the longitudinal center line of said sheet comprise a V-shaped rib projecting into said parabola in an approximate inversion of a vertex portion of said parabola, and an elongate heating element in said reflector located substantially at the focus of said parabolic section, said rib being arranged to reflect heat rays away from. said heating element.

2. A heater as in claim 1 wherein the cross-sectional width of said rib at its widest point is greater than the width of said heating element but not more than double the width of said heating element. 

1. In a radiant heater, a trough-shaped outer shell having inwardly directed flanges along the lateral edges thereof, said outer shell also having a plurality of vent openings therethrough, a trough-shaped reflector having outwardly directed flanges along the lateral edges thereof, said reflector including said flanges being within the trough formed by said shell and the flanges on said reflector being overlapped by the flanges on said shell, the surfaces of said reflector being spaced from the surfaces of the outer shell to form an air space therebetween, said reflector being positioned in said outer shell so as to reflect radiation through the open face of the trough-shaped outer shell, means securing each reflector flange to its adjacent overlapping flange on the shell, said last means comprising fasteners spaced at intervals along the length of said flanges, each fastener including a spacer positioned between the confronting faces of said flanges to maintain same in spaced relation to form lateral air inlet passageways between the spacers whereby air may flow into the space between the outer shell and reflector and thence out through the vent openings in the outer shell, the innermost edges of the flanges on said shell being spaced laterally outward from the innermost edges of the flanges on said trough-shaped reflector, said reflector comprising a unitary metal sheet bent along laterally spaced parallel lines to form elongated planar reflecting surfaces joined edge to edge in such angular relation that said reflector is approximately parabolic in transverse cross section, and the planar reflecting surfaces immediately adjacent to the longitudinal center line of said sheet comprise a V-shaped rib projecting into said parabola in an approximate inversion of a vertex portion of said parabola, and an elongate heating element in said reflector located substantially at the focus of said parabolic section, said rib being arranged to reflect heat rays away from said heating element.
 2. A heater as in claim 1 wherein the cross-sectional width of said rib at its widest point is greater than the width of said heating element but not more than double the width of said heating element. 